Dominant controls on catchment water quality dynamics: A Germany-wide analysis using data-driven models

提供清洁水是联合国2030年全球可持续发展目标之一。在中欧和德国，向地表水、地下水以及最后向海洋环境增加营养物的投入仍然是水生生态系统和供水的线索。在流域尺度上，大量相互关联的过程和输入途径阻碍了有效管理所需的机制理解和明确的因果关系。在过去的几十年里，人们在改善污水处理方面付出了巨大的努力，以减少地表水中磷和氮的点源输入。然而，来自农业来源的分散投入仍然很重要，而且由于运输时间滞后和遗留效应，难以管理。因此，减少农业氮过剩的措施对下游水质的影响往往难以预测。该提案利用了德国各地水质和水量的独特数据集。这些数据是基于德国联邦各州的定期水质监测，并由UFZ汇编而成。通过数据驱动的分析，利用浓度和浓度-流量关系的模式来总结流域尺度上的主导过程和输入路径。该提案侧重于三个目标：(a)对过去几年（低于2010年）的营养物质出口制度进行集水区分类。(b)随着输入途径的变化，氮磷比在较长时间序列上的时间发展。(c)集水区营养物输出的长期轨迹和向化学平衡条件发展的可能性。创新的数据驱动方法和独特的数据集允许对中欧人为改变景观环境中营养物质出口的主导控制有新的看法。研究结果将为在集水区尺度上建立复杂性降低的水质模型提供一个起点。此外，结果将对更广泛的学科，如水生生态学和环境管理感兴趣。

The availability of clean water is one of the United Nations global goal for sustainable development 2030. In Central Europe and Germany elevated inputs of nutrients to surface water, groundwater and finally to marine environments is still a thread for aquatic ecosystems and water supply. At catchment scale the multitude of interrelated processes and input pathways hinder a mechanistic understanding and a clear cause-effect relationship that is needed for effective management. In the last decades great efforts have been put into the improvement of wastewater treatment to reduce point source inputs of phosphorus and nitrogen into surface waters. However, diffuse inputs from agricultural sources are still important and hard to manage as a result of long transport time lags and legacy effects. Consequently, the effects of measures to reduce nitrogen surplus from agriculture on the downstream water quality are often hard to predict. This proposal utilizes a unique dataset of water quality and water quantity across Germany. This data is based on the regular water quality monitoring of Germany's federal states and was compiled by the UFZ. By means of a data-driven analysis, patterns in the concentration and concentration-discharge relationships are used to conclude on dominant processes and input pathways at catchment scale. The proposal focusses on three aims: (a) The classification of the catchments with regards to nutrient export regimes for the last years (younger than 2010). (b) The temporal development of nitrogen:phosphorus ratios for longer time series with changing input pathways. (c) The long-term trajectories of nutrient exports from catchments and the possible development towards chemostatic conditions. The innovative data-driven methods and the unique dataset allow a new view of dominant controls of nutrient exports in the Central-European settings of anthropogenically modified landscapes. The results will be a starting point for complexity reduced water quality model at catchment scale. Moreover, results will be of interest to a broader range of disciplines such as aquatic ecology and environmental management.